Recently, a polymeric composition including a polymeric monomer, a filler a polymerization initiator and so on is widely used as a repairing material in clinical dentistry. When dental polymeric compositions are classified depending upon the type of polymerization initiator, namely, the type of polymerization method, they are classified into photopolymerization type compositions, chemical polymerization type compositions and dual cure type compositions cured through both photopolymerization and chemical polymerization. Alternatively, when the dental polymeric compositions are classified depending upon the packing form, they are classified into one-paste type compositions and two-paste type compositions.
A photopolymerization type composition using a photopolymerization catalyst as a polymerization initiator is a 1-paste type composition. Owing to recently remarkably developed light irradiators, a photopolymerization type composition is widely used in the clinical dentistry. However, a photopolymerization type composition cannot be used for a repair portion that cannot be irradiated with light of a light irradiator, such as a bottom of a root canal portion or an inner face of the repairing material.
With respect to a chemical polymerization type composition or a dual cure type composition using, as a polymerization initiator, a redox catalyst composed of an oxidant and a reductant, the oxidant and the reductant are preferably packed in different packages for securing storage stability. Therefore, such a composition is generally a two-divided type composition, namely, a two-paste type composition.
In using a chemical polymerization type composition, two kinds of pastes are mixed with a tool such as a spatula or a mixing rod so as to cause a reaction between the oxidant and the reductant, and thus, the composition is polymerically cured. Although a chemical polymerization type composition can be advantageously used in a repair portion that cannot be irradiated with light, it is disadvantageously difficult to adjust its polymeric curing time.
A dual cure type composition is a dental polymeric composition developed for overcoming the disadvantage of the chemical polymerization type composition. In a dual cure type composition, a portion that cannot be irradiated with light is cured by using a redox catalyst, and a portion that can be irradiated with light is cured in a short period of time by using a photopolymerization catalyst that can be easily adjusted in the polymeric curing time. A dual cure type composition is also used as a core build-up material for repairing a root canal portion in which a root canal is formed after taking out a dental pulp of a tooth root where dental caries has been seriously advanced.
Examples of a commercially available dual cure type core build-up composition of the two-paste type are “UniFil-Core” (manufactured by GC Corporation; trade name), “LuxaCore-Dual” (manufactured by Dental-Material Gesselschaft mbH; trade name) and “Build-it FR” (manufactured by Generic Pentron; trade name).
On the other hand, Patent Document 1 describes a dental curable composition including a polymeric monomer, a filler with an average particle diameter of 0.05 through 1 μm, a fine particle filler with an average particle diameter smaller than 0.05 μm and a polymerization initiator. The curable composition described in Patent Document 1 is applied on a tooth neck or a tooth root in a small thickness with a small brush or the like, so as to form a cured coat on the tooth neck or the tooth root. Therefore, it is significant that the composition has both such low viscosity that it can be applied in a small thickness with a small brush and such low flowability that it can be prevented from flowing when applied. It is noted that Patent Document 1 does not mention a core build-up material at all and describes neither that the curable composition is a dual cure type composition nor that it is prepared from two pastes.
Patent Document 1 Japanese Laid-Open Patent Publication No. Hei 11-335220